Philosophy 4610
Carnap: “Psychology in Physical Language”
Last time, we saw how a certain way of looking at language can change our thinking
about the mind and give us reasons to doubt the Cartesian dualist picture. This time we’ll
consider another, related linguistic approach: the approach of logical behaviorism, which
is also anti-Cartesian in a similar way. Logical behaviorism denies that there are two
kinds of substances and two kinds of worlds, the mental and the physical; for logical
behaviorism, there is only one world, and it is describable in scientific language,
ultimately in the language of physics.
1. The approach of behaviorism. According to logical behaviorism, to talk about the
mind just is to talk about the behavior of the body. Consider some instances of “mental
talk” or talk “about minds”, what Carnap calls “sentences of psychology”:
He hopes that he will pass the test
He is angry
She is thinking about her future
He has a toothache.
According to behaviorism, all these sentences are translatable into sentences in a physical
language: that is, a language that describes bodies and matter only, and can ultimately be
reduced to the science of physics. None of them actually make reference to minds that
are distinct from the body, even if they seem to. We can translate each of these sentences
– or we will be able to, anyway, when our sciences progress far enough – into sentences
characterizing only matter and behavior, that is, into sentences characterizing only the
physical actions of bodies in space.
This might seem implausible at first. But consider how we know each of these sentences.
Suppose you storm into the room, yelling and shaking your fist. How do I know that you
are angry? I know that you are angry from your behavior, from the way I see your body
moving and the physical sounds I hear coming from your mouth. And in general, as we
saw last time also, we know about “other minds” from behavior alone. So Carnap’s
suggestion is that we can translate sentences that seem to be about minds and mental life
into sentences about behavior.
This is like our procedure in other sciences as well. We go from what we see or perceive
to the underlying things that explain what we see or perceive. Thus we go from our
observation that the wooden support is of a certain color and form, to the conclusion that
it is firm. Similarly, Carnap thinks (p. 42) that we can go from our perception of the
behavior of a person, to the conclusion that they are excited.
2. Non-occurent states and dispositions. This makes sense of how we might translate
from a sentence about one’s current, exhibited mental states to sentences about behavior.
For instance, we can translate from “he is angry” to “he is yelling, his fist is shaking,
etc.” But what about mental states that are not currently exhibited. Mr. A might be
angry, even though he is not showing it. Or suppose Mr. A knows how to ride a bicycle.
I can say “he knows how to ride a bicycle” even when he is not riding a bicycle. What do
I mean by this?
I mean something of a dispositional nature. That is, in saying that someone can ride a
bicycle, I am not saying what is happening right now, but I am saying what would happen
under certain circumstances. For instance, I am saying that if we brought him a bicycle
and told him to ride, he would ride it without falling down. Now, how can we translate
this kind of sentence into the physicalist language?
Carnap suggests that the case is analogous to other dispositional sentences that are
already in the physical language. For instance, suppose I say that this glass is fragile. To
say that the glass is fragile is to say something like: if the glass were dropped, it would
(most likely) break. This is analogous to the statement about the bicycle-rider: if he were
brought a bicycle, he would (most likely) ride it without falling over. And in both cases,
we can reduce the dispositional sentence to a sentence in the physical language. IN the
glass case, we know that to say that it is fragile is also to say that it has certain structural
properties that make it liable to break. We can give an account of these properties in
purely physical terms. Similarly, we translate the sentence about the bicycle-rider into a
description of the underlying properties of his body, nervous system, and brain that make
him capable of riding a bicycle. We may not know what these properties are yet, but
there is no problem in principle with finding them out. When we do, we will be able to
reduce all of our statements using “mental” language to statements in the physical
language, and we will have shown that we need not invoke anything beyond the world of
matter.
3. The illusion of dualism. Like Ryle, Carnap has an account of why we think dualism
is true, even if it isn’t. For Carnap, we think dualism is true largely because psychology
hasn’t yet progressed as far as other sciences. But when it does, we will be able to see
that there is no reason why we cannot translate sentences in ‘psychological’ or ‘mental’
language into sentences in the unified, physical language. Think again about the analogy
between the sentence about the glass being fragile and the sentence about Mr. A being
able to ride a bicycle. Now we know that the sentence about the glass being fragile can
be reduced to a sentence about the underlying physical properties of the glass. We know
which kinds of glass are fragile, and which are not, and why. But before we knew this,
we might think that fragility is just an extra, special kind of power or property that the
glass has. We might think that, above and beyond all its physical properties, it has the
non-physical property of fragility. And we might even introduce a separate kind of
existence or substance to be the bearer of this property.
According to Carnap, this is the situation we are in with respect to the ‘mental.’ We
don’t yet understand the underlying physical story, so we are tempted to think that there
is a non-physical story that goes alongside the physical one. But this is just as much a
confusion as the parallel thought about fragility would be. There’s no more reason to
believe that the mind is an additional substance, over and above the body, then there is to
believe that “fragility” is an extra, non-physical property, over and above the properties
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of the physical glass. As science progresses, we will understand in greater detail how to
reduce our ordinary sentences about ‘the mind’ to sentences characterizing the behavior
and underlying physical states of the people we are describing. Psychology will become
a chapter of the unity of science, ultimately reducible to a universal, physical description
of the world, and we will eliminate the mystification and confusion of the Cartesian
dualist worldview.
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